1. Field of the Invention
The present invention relates generally to vehicle occupant sensing systems and, more specifically, to such a system having a circuit carrier tray adapted to properly orient a plurality of sensor assemblies.
2. Description of the Related Art
Automotive vehicles employ seating systems that accommodate the passengers of the vehicle. The seating systems include restraint systems that are calculated to restrain and protect the occupants in the event of a collision. The primary restraint system commonly employed in most vehicles today is the seatbelt. Seatbelts usually include a lap belt and a shoulder belt that extends diagonally across the occupant's torso from one end of the lap belt to a mounting structure located proximate to the occupant's opposite shoulder.
In addition, automotive vehicles may include supplemental restraint systems. The most common supplemental restraint system employed in automotive vehicles today is the inflatable airbag. In the event of a collision, the airbags are deployed as an additional means of restraining and protecting the occupants of the vehicle. Originally, the supplemental inflatable restraints (airbags) were deployed in the event of a collision whether or not any given seat was occupied. These supplemental inflatable restraints and their associated deployment systems are expensive and over time this deployment strategy was deemed not to be cost effective. Thus, there became a recognized need in the art for a means to selectively control the deployment of the airbags such that deployment occurs only when the seat is occupied.
Partially in response to this need, vehicle safety systems have been proposed that include vehicle occupant sensing systems capable of detecting whether or not a given seat is occupied. The systems act as a switch in controlling the deployment of a corresponding air bag. As such, if the occupant sensing device detects that a seat is unoccupied during a collision, it can prevent the corresponding air bag from deploying, thereby saving the vehicle owner the unnecessary cost of replacing the expended air bag.
Furthermore, many airbag deployment forces and speeds have generally been optimized to restrain one hundred eighty pound males because the one hundred eighty pound male represents the mean average for all types of vehicle occupants. However, the airbag deployment force and speed required to restrain a one hundred eighty pound male exceeds that which are required to restrain smaller occupants, such as some females and small children. Thus, there became a recognized need in the art for occupant sensing systems that could be used to selectively control the deployment of the airbags when a person below a predetermined weight occupies the seat.
Accordingly, other vehicle safety systems have been proposed that are capable of detecting the weight of an occupant. In one such air bag system, if the occupant's weight falls below a predetermined level, then the system can suppress the inflation of the air bag or will prevent the air bag from deploying at all. This reduces the risk of injury that the inflating air bag could otherwise cause to the smaller-sized occupant.
One necessary component of each of the known systems discussed above includes some means for sensing the presence of the vehicle occupant in the seat. One such means may include a sensor device supported within the lower seat cushion of the vehicle seat. For example, U.S. published patent application having U.S. Ser. No. 10/249,527 and Publication No. US2003/0196495 A1 filed in the name of Saunders et al. discloses a method and apparatus for sensing seat occupancy including a sensor/emitter pair that is supported within a preassembled one-piece cylinder-shaped housing. The housing is adapted to be mounted within a hole formed in the seat cushion and extending from the B-surface toward the A-surface of the seat cushion. The sensor/emitter pair supported in the housing includes an emitter that is mounted within the seat cushion and spaced below the upper or A-surface of the seat cushion. In addition, the sensor is also supported by the housing within the seat cushion but spaced below the emitter. The cylindrical housing is formed of a compressible, rubber-like material that is responsive to loads placed on the upper surface of the seat cushion. The housing compresses in response to a load on the seat cushion. The load is detected through movement of the emitter toward the sensor as the housing is compressed. The housing is sufficiently resilient to restore the emitter to full height when no load is applied to the upper surface of the seat cushion. The Saunders et al. system also includes a processor for receiving the sensor signals and interpreting the signals to produce an output to indicate the presence of an occupant in the seat.
While the Saunders et al. occupant seat sensing system teaches a sensor/emitter pair that may sense the presence of a vehicle seat occupant, it suffers from certain disadvantages associated with the fact that it is mounted within the seat cushion of the vehicle seat. For example, vehicle seat cushions typically employ a foam or other cushiony material of a predetermined thickness. The thickness of this material is preferably calculated to provide adequate comfort for the occupant. However, with the housings of the sensor/emitter pairs mounted within the cushion, the occupant may feel one or more of the housings through the seat cushion. This is especially true over time as the seat cushion becomes worn. Furthermore, while the compressible, rubber-like housing taught by Saunders et al. is generally responsive to forces extending along the length of its axis, is also subject to transverse or “shear” forces acting through the seat cushion. Thus, the housing can be deformed in an irregular manner resulting in false readings generated by the sensor/emitter pair.
In addition to providing occupant restraint systems, vehicle seats must satisfy governmental motor vehicle safety standards, such as those found in 49 C.F.R. §§ 571.207–208 (2003). Particularly, some safety standards address the seat's ability to retain an occupant in the seat during a collision. In partial response to such standards, vehicle seat manufacturers angle the front portion of the lower seat cushion and the seat pan that supports the lower seat cushion. These components are angled toward the occupant such that they bear some of the occupant's forward inertial load in the event of a sudden deceleration. In some cases, however, angling the front portion of the seat pan can cause the sensing means to be subject to excessive shear loading. Such loading may inhibit the operation of these sensor assemblies and can result in a false reading.
Therefore, there is an ongoing need in the art for a circuit carrier tray for a vehicle occupant sensing system that acts to properly orient the sensing means such that the sensing means is receptive primarily to axial weight loads regardless of the angularity of the seat pan on which it is positioned so as to ensure proper detection of occupants in the vehicle seat.